The transmission system used on snowmobiles and some other recreational vehicles (commonly known as constantly variable transmissions, or "CVT"s) uses a clutch mechanism that incorporates weights and springs to provide engagement by centrifugal force at a predetermined engine speed. This speed is set by the use of movable weights and spring tension in the drive (primary) pulley in a belt and pulley set. The exact arrangement of the weights and spring(s) varies between manufacturers, but all operate similarly in principle and physical motion.
These constant variable transmission devices are well known to those skilled in the art and are disclosed, e.g., in U.S. Pat. No. 4,934,217 of Biem, the entire disclosure of which is hereby incorporated by reference into this specification. Reference may also be had to U.S. Pat. No. 4,991,400 of Wilkinson, whose disclosure is also hereby incorporated herein by reference.
One characteristic of the constant variable transmission system is the fixed engagement speed, and the need to accelerate the engine to this speed to cause actual engagement. Although this is normally not a significant weakness, there are cases when exact control of this engagement is desirable. The main example of this is in racing, where the ability to leave the starting line predictably is a major factor in success. The need to accelerate the engine from some point below engagement through the engagement speed is an imprecise operation in relation to the frame of time needed to ideally accomplish clutch engagement (several tenths of a second).
To the best of applicant's knowledge, none of the prior art devices provides the capability of manually engaging the clutch at speeds below the fixed engagement.
It is an object of this invention to provide a manual actuator that will give the operator the ability to engage the clutch at any time, independent of engine speed.
It is a further object of this invention to provide a manual actuator which will not interfere with the other aspects of operation of the constant variable transmission.
It is a further object of this invention to provide a manual actuator which is small enough to fit within the space available in the body of the vehicle. The amount of space available is set by the need to be able to remove the primary clutch without removing the engine from the vehicle, nominally 1.5 inches, with allowance for additional extension along the centerline of rotation.